Authors:Gianfranco Caruso, Luisa FerroniPages: 131 - 143Abstract: CFD can be used both in the design phase and in the performance assessment phase, for example in the evaluation of the performance of safety and fire protection systems in the presence of fires of different intensity, duration and location. Several and detailed results can be obtained from these analyses, e.g. velocity fields, temperatures and concentrations of smoke and gases in the 3D computational domain, even in transient conditions. In the paper, a detailed analysis has been carried out using a general purpose CFD code (FLUENT v. 6.3.26), with the objective to demonstrate the capability of this widely used code in assessing, in addition to the thermal-fluid dynamic field of the smoke, useful parameters concerning tenability criteria and visibility. The limitations that must always be considered in evaluating the results obtained by using these numerical tools have been evidenced. The analysis was conducted inside a typical store in a commercial building in order to obtain a preliminary assessment of the effectiveness of the extinguishing systems (i.e. the sprinkler system) in limiting the temperature and the concentrations of toxic gases (tenability criteria) and assuring acceptable visibility into the environment, to guarantee a safe evacuation of workers and public from the burned store.PubDate: 2015-01-16Issue No:Vol. 6, No. 4 (2015)

Authors:Mahmoud Haasean NasefPages: 144 - 158Abstract: This paper discusses numerically a modified Savonius wind rotor focusing on the averaged torque and power coefficients over a complete cycle of operation. The numerical study is performed using the commercial software Fluent 6.3.26 with four different turbulence models. The computations are tested against available experimental data to choose the suitable turbulence model and hence to extend the numerical investigation. A modification process of the Savonius rotor blades is designed by determining nine points on the perimeter of the blade. The two points at the ends of the blade are fixed in the same locations and the other seven points are moving to different locations to generate four polynomials shapes. V- shape blade rotor with three different V- angles is also studied in this paper. The influence of the rotor blade modification is checked based on the torque and power coefficients, keeping the Reynolds number, based on rotor diameter constant. The results obtained for the classical Savonius rotor are in agreement with the published experimental data, indicated that the method can be successfully used for such analysis. The theoretical results indicate that one of the polynomial blade shape has the best performance. PubDate: 2015-01-16Issue No:Vol. 6, No. 4 (2015)

Authors:Arabi Radwan, Kamal A Ibrahim, Ahmed Hanafy, Khalid M SaqrPages: 159 - 174Abstract: This article presents numerical simulations of unconfined swirl flow. The Sydney swirl flow database was used as references for the boundary conditions and experimental validation. A number of RANS turbulence models were investigated in order to explore their potential in predicting axial and swirl velocity profiles of the swirl flow field. The numerical investigations showed that among the tested RANS models, the k-w showed an acceptable performance in predicting the swirling flow features in both cases (low and high swirl level). The results also demonstrated that the k-w model was able to provide a reasonably accurate prediction data that is in consistent with experimental measurements at most locations. PubDate: 2015-01-16Issue No:Vol. 6, No. 4 (2015)

Authors:Gasser Elhussien Hassan, Amany Hassan, Mohamed Elsayed YoussefPages: 175 - 187Abstract: This study is concerned with investigating the accuracy of different two-equations turbulence models based on eddy-viscosity concept which are widely used to simulate the aerodynamics characteristics of Vertical Axes Wind Turbines (VAWT) with straight blades. The investigated models are Standard, RNG and Realizable k–ε, Standard and SST k–ω models. The medium range of Reynolds numbers between 300,000 and 1000,000 and angle of attack between 0 and 25 are studied for NACA 0018 airfoil. This covers an important range of operation for VAWT. Due to the lake of the VAWT measured data, the predicted numerical results for static aerodynamics characteristics of NACA 0018 airfoil, namely CL, CD, critical angle of attack and CLmax, are compared with the available experimental data for static NACA0018 by Jacobs and Sherman (1937)[1], Shedahl and Klimas (1981)[2] and Timmer (2008) [3]. The study shows that the k–ω SST model is the most accurate model compared with all the investigated models for all the investigated range of Re numbers and angle of attack.PubDate: 2015-03-02Issue No:Vol. 6, No. 4 (2015)